Question about 2002 Yamaha DT 125 R

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Dt 230 low on gets half revs then runs

My dt 230 starts well and runs good at low revs. HOWEVER at about half revs it feels like it hits a rev limiter and starts to run rough and no power left. I disconected the gear box speed sensor this stopped the rough running but it still lacked power. ( flat out at 80kph.) Is it the cdi unit or something else?

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Hi there, you likely still have the restrictor in the exhaust header. Mine was the same, they are shipped like that as standard. Take the exhaust off the engine and remove the the concentric tube that's in there (you need to cut it out). Instant +100% power, if that is your problem.

Posted on Mar 05, 2012


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Posted on Jan 02, 2017

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It does sound like an ignition timing problem, but could also be a breathing issue, air flow in or exhaust flow out could be restricted i.e.:dirty air filter, excessive carbon build up in exhaust pipe from burning too much oil or rich fuel mixture.
possibly and more likely some junk got into your fuel system and partially plugged up the main jet in the carb, -or has the needle on the slide been moved? The little circlip at the top of the needle, if it has one.
1.Replace the spark plug, check gap, check spark, it should be bright blue and fat.
2. check the fuel filter, if no filter check the carb for dirt.

Posted on Jan 20, 2009

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SOURCE: yamaha dt 200 won't rev off idle

You should measure the combustion ratio.Maybe piston rings failed.

Posted on Jun 03, 2009

  • 4 Answers

SOURCE: Yamaha Dt 125 mx 2 stroke won't rev out and lacks power

new points is a must !

Posted on Aug 17, 2009

  • 10 Answers

SOURCE: I have a 2003 Suzuki ltz 400 quad sport, when i

the stator wouldn't make it cut out.. do you know what rpm it's cutting out at. hey feel free to email me and i'll walk you through it and try to help you out.i'm pretty familiar with things of the nature... might even be a smaller fuel jet restricting you or a re stricter in the exhaust pipe or muffler or between the carb and head. give a shout and i'll try to help

Posted on Apr 26, 2010

Testimonial: "i changed the jet, that was the first the i was told it could be and (even though i didn't think that was the problem)it worked the bike runs awesome "

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Maybe this will help. This is a common problem that I have had with my GV250. Almost the same bike mechanically by Hyosung.

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Very prominant if running add on fog lights as well, like I do.
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